I am building a cabinet and I'm wondering if there is any opaque material which allows safe passage of IR? or do I need a IR extender?

Heck, the glass in my parents' cabinet won't even pass IR.

In a past home, I used an IR relay device, but it seems many newer remotes use RF to a remote device that sends the IR codes to each component somehow invisible to the infrared light beam.

RF will pass, in varying strengths, through walls and floors, but may suffer from interference from other devices, not all of which might be considered RF transmitters.

I use a Phillips Pronto with RF extender and it works from anywhere in my house.

Programming is a bit on the tricky side and I paid a local guy to do it for me but after looking over his shoulder I think I'm ready to try it myself.

It'll set you back around $500 but is well worth it if you need to operate the remote through cabinets (which I do).

I ordered the same cabinets as the rest of my house for my home theater. For the equipment, I had them leave the dorr panels out and had some custom perforated steel sheets cut by a local metal shop. The steel has small round holes punched out (similar to Salamander stands). IR goes right through. The steel panels came unfinished so I cleaned off the oil and sprayed them with gloss blackTremclad. It worked out very well. You might be able to order them directly from the cabinet maker to save time and effort. I would look into that if I do it again.

I use a Phillips Pronto with RF extender and it works from anywhere in my house.

Programming is a bit on the tricky side and I paid a local guy to do it for me but after looking over his shoulder I think I'm ready to try it myself.

It'll set you back around $500 but is well worth it if you need to operate the remote through cabinets (which I do).

I already have the Harmony 880 and love it.

Can anyone recommend a good IR extender to simply get my signals inside a cabinet?

I ordered the same cabinets as the rest of my house for my home theater. For the equipment, I had them leave the dorr panels out and had some custom perforated steel sheets cut by a local metal shop. The steel has small round holes punched out (similar to Salamander stands). IR goes right through. The steel panels came unfinished so I cleaned off the oil and sprayed them with gloss blackTremclad. It worked out very well. You might be able to order them directly from the cabinet maker to save time and effort. I would look into that if I do it again.

That's exactly what I want to do. I figured that some perforated cloth would work as well. Kinda like the fabric that Speakers are placed behind to keep them from sight.

Any contacts?